SymptomsWhen you launch Parallels Desktop you get the rainbow wheel spinning for several minutes and you cannot do anything with it until you quit Parallels Desktop with help of Activity monitor. Also, the Finder shows as being unresponsive, so you have to relaunch it as well.
CauseSuch situation could happen due to Smart Mount option enabled .
If there are some shared drives in the network which your Mac belongs to, when you start Parallels Desktop, it tries to connect to all of them, and mount them to the virtual machine. This procedure is performed normally except if some of the volumes are not available (for example, if the relevant computer is switched off). In this case Parallels Desktop is locked up while it tries to connect to them and locks the Finder as well.
ResolutionPlease, open the virtual machine's configuration, switch to Smart Mount tab and deselect the correspondent checkbox.
This is only a temporary workaround. The issue is under investigation and as soon as it is fixed it will be possible to enable Smart Mount again.